200619th International Lightning Detection Conference24-25 April • Tucson, Arizona, USA 1st International Lightning Meteorology Conference26-27 April • Tucson, Arizona, USA

Effect of active thunderstorms on ionospheric electron and ion temperatures as obtained by the SROSS-C2 satellite measurements

Jagdish Rai, D. K. Sharma, Ramesh Chand*, K. Suda & M. Israil* Department of Physics, Indian Institute of Technology, Roorkee, India

*Department of Earth Sciences, Indian Institute of Technology, Roorkee, India

jgraifph2003@yahoo.co.in/ dksphdes@rediffmail.com Fax: +91-1332-273560

1. Introduction The space weather changes are known to influence some of the tropospheric parameters

(Schunk and Sojka, 1996). On the other hand, the tropospheric disturbances are known to influence the

ionospheric parameters (Rai et al., 1973; Singh et al., 2001 and others). The purpose of present this

paper, is to see the influence of thunderstorms on ionospheric electron and ion temperatures.

The ionosphere has been studied extensively by many workers (Mahajan et al., 1983; Pasko et

al., 1995; Rai et al., 1972; Oyama et al., 1996; Singh et al., 2001and others) and different techniques

have been used. For the present study, the data has been obtained by Retarded Potential Analyzer

(RPA) payload aboard Indian SROSS-C2 satellite. The data for thunderstorms activity have been

obtained from India Meteorological Department. The solar flares data were obtained from National

Geophysical Data Centre (NGDC), Boulder, Colorado.

2. The Experimental Technique The RPA payload aboard SROSS-C2 satellite consists of two sensors viz., electron and ion

sensors and associated electronics (Garg and Das, 1995). The electron and ion RPAs are used for in situ

measurements of ionospheric electron and ion temperatures. Complete description of the RPA payload

has been given in Sharma et al., (2004). The SROSS-C2 satellite was launched by Indian Space

Research Organization (ISRO) on May 4, 1994 to study the ionospheric composition and temperature

anomalies. It has yielded valuable data on electron and ion temperatures over low latitude locations in the

altitude in range 425-625 km.

3. Data Analysis The data collected for the period from 1995-1998 has been analyzed for anomalous variations due to

thunderstorm activity in the altitude range from 425 to 625 km. The measurements corresponding to three

different locations viz. Bhopal (23.16° N, 77.36° E), Panji (15.30° N, 73.55° E) and Trivandrum (08.29° N,

76.59° E) were analysed.

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The recorded ionospheric temperature data were matched with the thunderstorm activity at different

locations. For the period of our interest, it has been found that seven events of thunderstorms correspond

to the satellite data. The recorded average electron and ion temperature during active thunderstorms

have been compared with the average normal days electron and ion temperature for the same time

interval. Care has been taken to select the satellite data, which is free from diurnal, seasonal, latitudinal,

longitudinal and altitude effects. The average of normal time electron and ion temperatures have been

made for a month, starting almost 15 days before the thunderstorm day and continuing to 15 days more

after that. Thus the possibility of seasonal effect has completely been ruled out because all data points

correspond to the same season. A window of 5° in latitude and longitude for the satellite observation at

the meteorological data center has enabled the latitudinal and longitudinal effect to be ineffective. The

averaging of electron and ion temperatures at nearly the same hours of the day as that of the active

thunderstorm has made it free from the diurnal effect. The analysis has been made for the altitude range

425 to 625 km only, thus making it independent of the altitude. Further, only those thunderstorm days

have been considered in this study, which are free from the solar flares. Care has also been taken to

choose the data only from those days, which are free from earthquakes.

In our studies only seven thunderstorm days have been found which correspond to the satellite

passes. However, in each satellite pass many data points were recorded at regular intervals. In all the

seven events 110 data points were obtained and in each case the electron and ion temperatures were

above the normal day observations. On many occasions during its passes above the thunderstorm, the

sensors could not record the electron and ion temperatures. All temperature data recorded by SROSS-C2

satellite are within the error limit of ± 50 K.

4. Results and Discussion

In 1995, two events were recorded corresponding to Bhopal (23.16° N, 77.36° E) and two to

Trivandrum (08.29° N, 76.59° E). Fig. 1 shows the comparison of electron temperature during

thunderstorms and normal days for the above incidents. At Bhopal, there were thunderstorms on January

11 and August 29, 1995. During these events the average electron temperature was enhanced by 1.2 to

1.3 times [Fig.1 (a, d)] over the normal day average electron temperature. However, at Trivandrum it was

enhanced by 1.2 to 1.4 times [Fig.1 (c, b)] during the active thunderstorms on April 13 and April 28, 1995

over the normal days. Fig. 2 shows the comparison of ion temperature during active thunderstorms and

those during normal days for the above four events. In 1995, the average ion temperature at Bhopal was

enhanced by 1.2 times [Fig.2 (a, d)] for both events and at Trivandrum it was enhanced by 1.1 to 1.5

times [Fig.2 (b, c)] during the thunderstorm activities.

Two events were recorded in 1997; one corresponding to Trivandrum on June 27 and another to

Bhopal (23.16° N, 77.36° E) on December 10. At Trivandrum, the average electron temperature was

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enhanced by 1.7 times (Fig. 3a) and at Bhopal it was enhanced by 1.4 times (Fig. 3b) during the active

thunderstorms as compared to the normal days. However, the average ion temperature was enhanced by

1.3 times [Fig. 4 (a, b)] to that of normal days temperature at both stations.

In 1998, one event has been found at Panji (15.30° N, 73.55° E). There were two active

thunderstorms recorded during two consecutive days (August 15 and 16) at the same time. The average

electron temperature was enhanced by 1.5 times (Fig. 5) and the average ion temperature by 1.3 times

(Fig. 6) to that of normal days temperature.

The above analysis shows that there is a consistent enhancement of ionospheric electron and ion

temperatures recorded during active thunderstorms period. This enhancement was for the average

electron temperature ranging from 1.2 to 1.7 times compared to the average normal day’s temperature.

However, for ion temperature this enhancement was from 1.1 to 1.5 times. It is once more emphasized

that in the present study the data were selected in such way that the effect of diurnal, seasonal,

latitudinal, longitudinal and altitude effects were minimum. Thus the temperature enhancements are

directly related to the thunderstorm events.

The enhancements in ionospheric electron and ion temperatures have been attributed to the

lightning activity associated with thunderstorms. It has been proposed that the phenomena like sprites,

blue jets, blue starters, elves and others (Pasko et al., 1996, 1997; Sentman et al., 1995; Bell et al., 1995)

may generate radiations from ULF to VLF range (Inan et al., 1991, 1996; Otsuyama et al., 1999), which

may heat the plasma in the ionosphere above thunderstorms. However, any authentic work in this area

must include the detailed theoretical calculations, which is beyond the scope of this paper.

5. Conclusions The present study reveals that the electron and ion temperatures show a consistent

enhancement during the thunderstorm events. The enhancement in case of electron temperature is

slightly higher than the enhancement of ion temperature during the active thunderstorms over the normal

days.

Acknowledgements

The present study has been financed by the Indian Space Research Organization, Bangalore and

Council of Scientific and Industrial Research, New Delhi. The authors are thankful to India Meteorological

Department for providing the valuable data on thunderstorm activity and NGDC, Boulder, USA for

providing the data on solar flares.

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References Bell, T. F., Pasko, V. P., Inan, U. S., 1995. Runaway electron as a source of Red Sprites in the mesosphere. Geophys Res Lett, 22, 2127-2130. Garg, S. C., Das, U. N., 1995. Aeronomy experiment on SROSS-C2. J. Spacecraft Technology, 5, 11-15. Inan, U. S., Bell, T. F., Ridriguez, J. V., 1991. Heating and ionization of the lower ionosphere by lightning. Geophys Res Lett, 18, 705-708. Inan, U. S., Pasko, V. P., Bell, T. F., 1996. Sustained heating of the ionosphere above thunderstorms as evidenced in “early/fast” VLF events. Geophys Res Lett, 23, 1067-1070. Mahajan, K. K., Panday, V. K., Jain, V. C., 1983. Relationship between electron density and electron temperature as a function of solar activity. Adv Space Res, (U. K.) 2, 247-249. Otsuyama, T., Hobara, Y., Hayakawa, M., 1999. EM radiation associated with sprites. Proc. 11th

International conference on Atmospheric Electricity held at Alabama (USA), 96-98. Oyama, K. I., Watanabe, S., Su, Y., Takahashi, T., Hirao, K., 1996. Season, local time and longitudinal variations of electron temperature at the height of ~600 km in the low latitude region, Adv. Space Res., 18, 269-278. Pasko, V. P., Inan, U.S., Bell, T. F., Y. N. Taranenko, 1995. Heating, ionization and upward discharges in the mesosphere due to intense quasi-electrostatic thundercloud fields. Geophys Res Lett, 22, 365-368. Pasko, V. P., Inan, U. S., Bell, T. F., Taranenko, Y. N., 1996. Sustained heating of the ionosphere above thunderstorms as evidenced in “early/fast” VLF events. Geophys Res Lett, 23, 1067-1070. Pasko, V. P., Inan, U. S., Bell, T. F., Y. N. Taranenko, 1997. Sprites produced by quasi-electrostatic heating and ionization in the lower ionosphere. Journal of Geophys Res, 102, 4529-4561. Rai, J., Rao, M., Tantry, B. A. P., 1972. Bremsstrahlung as a possible source of UHF emission from lightning. Nature (Physical Science), 238, 50-60. Rai, J., Bhattacharya, P. K., Sapru, M. L., 1973. Ionospheric disturbances due to thunderstorms. Int. J. Electronics, 34(6), 757-760. Schunk, R. W., Sojka, J. J., 1996. Ionosphere-thermosphere space weather issue, Journal of Atmos & Solar Terr Phys, 58(14), 1527-1574. Sentman, D. D., Wescott, E. M., Osborne, D. L., Hampton, D. L., M J Heavner, 1995. Preliminary results from the Sprites 94 aircraft campaign: 1. Red Sprites. Geophys Res Lett, 22, 1205-1208. Sharma, D. K., Rai, J., Israil, M., Subrahmanyam, P., Chopra, P., and S. C. Garg, Enhancement in ionospheric temperatures during thunderstorms, Journal of Atmospheric & Solar Terrestrial Physics, 66 (2004) 51-56. Singh, R. P., Patel, R. P., 2001. Lightning generated ELF, VLF, Optical waves and their diagnostic features. Proc. National workshop on Recent Developments in Atmospheric and Space Sciences, IIT Roorkee, 9-32.

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Ele

ctro

n Te

mp.

, (K

)

Local Time (hrs)

Figure 1 Electron Temperature variations for the events recorded at Bhopal (a, d) and at Trivandrum (b, c) in 1995.

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Local Time (hrs)

Ion

Tem

p., (

K)

Figure 2 Ion Temperature variations for the events recorded at Bhopal (a, d) and at Trivandrum (b, c) in 1995.

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Local Time (hrs)

Ele

ctro

n Te

mp.

, (K

)

Figure 3 Electron Temperature variations for the events recorded at Trivandrum (a) and at Bhopal (b) in 1997.

Local Time (hrs)

Ion

Tem

p., (

K)

Figure 4 Ion Temperature variations for the events recorded at Trivandrum (a) and at Bhopal (b) in 1997.

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Local Time (hrs)

Ele

ctro

n Te

mp.

, (K

)

Local Time (hrs)

Figure 5 Electron Temperature variations for the events recorded at Panji in 1998.

Ion

Tem

p., (

K)

Figure 6 Ion Temperature variations for the events recorded at Panji in 1998.

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